Implement RFC 8414 for OAuth 2.0 server metadata (#29191)

app/serializers/oauth_metadata_serializer.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class OauthMetadataSerializer < ActiveModel::Serializer
+  attributes :issuer, :authorization_endpoint, :token_endpoint,
+             :revocation_endpoint, :scopes_supported,
+             :response_types_supported, :response_modes_supported,
+             :grant_types_supported, :token_endpoint_auth_methods_supported,
+             :service_documentation, :app_registration_endpoint
+end